Author's reply

The Schizophrenia Quality of Life Scale (SQLS) is a measure of quality of life based on statements made by people with schizophrenia. We asked participants to state how their quality of life was affected by their mental health and the result was a mixture of symptoms, side-effects and psychosocial issues. Naturally, there is an overlap in the use of these terms, but our method elicits responses related to quality of life from a patient's perspective.

We believe that nobody can know their quality of life better than the person him- or herself. We have no reason to believe, on the basis of our findings, that people with schizophrenia are incapable of accurately representing their quality of life using the SQLS. It is of interest that we found that the people we interviewed voiced a variety of concerns, albeit not about possible financial and accommodation problems, which are, in any event, objective issues.

The measurement of quality of life is in the scientific domain and different methods, whether by questionnaire or interview, need to demonstrate reliability and validity. Thereafter, the choice of instrument requires a trade-off, representing a decision about the best instrument for a particular purpose. Factors such as ease of use, acceptability and cost must be considered.

In contrast to measures such as the Manchester Short Assessment of Quality of Life (MANSA), the SQLS has been specifically developed from interviews with people with schizophrenia, as opposed to being based on other measures. It was also developed as a measure for use in clinical trials and other research studies, as opposed to the assessment of community programmes, which is the case with the Lancashire Quality of Life Profile (Oliver et al, 1996), the measure from which the MANSA was derived. We would emphasise that the administration procedures contained in The User Manual for the SQLS (available from Oxford Outcomes) recommend, among other things, that the SQLS is completed in the presence of the researcher or is administered as an interview if the patient has difficulty with self-completion.

The SQLS has been very well received by colleagues both in the UK and internationally and the development of the instrument is continuing. It is clear to us from the response so far that the SQLS is recognised to fulfil a significant clinical and research need in relation to the assessment of quality of life in people with schizophrenia.